Users of mobile electronic devices such as cell phones, MP3 players, and lap top computers often utilize a number of different headphone type devices for listening to the audio output of their electronic devices. For example, a user may have a headset/microphone combination for use with voice communication or conferencing in the workplace. The same user may have stereo headphones for music listening, and perhaps “ear bud” devices for use while exercising.
The use of all these different headphone type listening devices with a single portable electronic device can have compatibility issues. Firstly, the sensitivity varies considerably from manufacturer to manufacturer and product type to product type. The sensitivity is the measure of the amount of voltage (or power) needed to produce a given sound pressure level (SPL) in the user's ear. Swapping a high sensitivity headphone device subsequent to the use of a low sensitivity device may cause pain and ear damage due to the high SPL produced at the volume setting previously used with the low sensitivity device. Secondly, the impedance of various headphone listening devices can vary almost three orders of magnitude, from about 10 ohms to nearly 1000 ohms. This impedance variation can require different amplifier gain settings for optimum operation. Thirdly, headphone devices may require customized frequency equalization (EQ) for the best sound performance. Equalization is the process in which the frequency response of the headphone device is altered to better suit the listening requirements of the user. Preset tonal settings (e.g. “rock”, “jazz”, etc.) are often used.
Attempts have been made to have an electronic device try to determine the type of headphone that is being used. These attempts often involve a making a simple DC resistance measurement of the headphone. Unfortunately, this type of measurement is inadequate to distinguish accurately between the large number of headphone devices and their sensitivity or equalization requirements.
These and other limitations of the prior art will become apparent to those of skill in the art upon a reading of the following descriptions and a study of the several figures of the drawing.